US Coast Guard, RD-4 Dolphin
Douglas Aircraft Company, RD-4 Dolphin: Ten aircraft for the US Coast Guard. They were similar to the RD-3 but had increased fuel capacity and were powered by two 420 hp (313.2 kW) Pratt & Whitney R-1340-CI nine-cylinder, single row, air-cooled radial engines. These aircraft were delivered between November 1934 and April 1935.
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